Juan Williams, Fox News analyst, the Hill columnist and author of "What the Hell Do You Have to Lose?" joined Fox News Radio's Marie Harf to discuss birthright citizenship and the midterms.

On why Trump decided to bring up birthright citizenship now: The thing is when you look at numbers the Republican base is very sensitive to immigration. Immigration doesn't even rank as an issue among Democrats or Independents for that matter, but among Republicans it is like the number two or three top issue in the midterms and I think that's why the President does that. (3:58)

On if he thinks Trump's closing argument will work: Today the pollsters were digging on this, especially here at Fox and here's what the polls show. The polls show that in 2016 Republicans were more trusted on immigration than Democrats. But today the most recent polls show that it has switched. Now Democrats are more trusted on immigration than Republicans. What has happened in the intervening time? I think it's Donald Trump's focus on immigration, the beating up of immigrants. (6:25)

On Obamacare being more popular than the tax cuts: Obviously I think people came to the conclusion that it didn't put money into their pocket and they're wondering where the money went. There's also the explosion of the deficit. So, I think it downplays some of the potential advantage Republicans might have gained from the idea of hey we come in and we cut taxes and that's always been a Republican tried and true strategy. But the second part of that is that I think that they don't appreciate the idea that people really want protection for themselves and their families against some catastrophic medical emergency leading to bankruptcy or close to it and they've seen some of the benefits of Obamacare come to fruition. (8:32)

On what races he's focused on: I think that what's going on in Texas is pretty amazing to me. As you know Senator Cruz is there in a Republican state. You would think there really wasn't going to be much of a challenge that has changed in the last month. Suddenly it was the case that Beto O'Rourke was within single digits of Senator Cruz. Then Cruz had a resurgence and he went back up in some polls by double digits, but now it's back in the latest polls to about five points. And as you know Beto O'Rourke has raised a record amount of money for a Senate race. That's how much intensity is involved there. (12:37)